Heat treatment furnace with crown-shaped transport path for the workpieces

ABSTRACT

In a heat treatment furnace with a circular charge conveyor system, bar-shaped charge support elements are provided and said support elements are mobile with respect to each other both in a vertical direction and in the direction of charge travel. Said support elements are arranged substantially in a radial direction and/or in a circle or in sectors of a circle. Several such charge support elements arranged radially are preferably assembled to form fork-type elements. Said support elements may also be arranged in a plurality of vertical planes to form a continuous or a discontinuous helical-type charge conveyor system. The present invention increases throughput, if compared with a conventional furnace of the same size, reduces energy requirements and thus improves conventional pusher-type furnaces for heat treatment in a controlled atmosphere.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a furnace wherein the charge ofworkpiece is carried during heat treatment by a circular conveyorsystem.

2. Description of the Prior Art

Similar furnaces are known as rotary hearth furnaces consisting of acylindrical or a rectangular furnace chamber and a rotating hearth, thecharge to be treated being placed on the slowly turning hearth andtravelling on said moving hearth through the different furnace zones.The hearth is mounted on bearings outside the furnace and rotated by adrive mechanism also located outside the furnace. Rotary hearth furnacesare usually operated in a cycle mode and can only be charged when apiece has been removed from the furnace. The charged piece travelsstepwise from the furnace entry through the heating zone and the soakingzone to the furnace outlet.

The use of such rotary hearth furnaces has become a standard practicefor heat treatment, but it is impossible to adjust the length of arotary hearth furnace cycle. A given time is hence always required for acertain charge to travel through a given rotary hearth furnace, therotary hearth furnace design thus determining the length of the heattreatment cycle.

It is further difficult to implement gas treating processes such asnitriding in rotary hearth furnaces, since the time during which thecharge remains in the soaking zone is usually too short. Moreover, eachhot tray carrying the heat-treated charge rests in the immediatevicinity of a cold tray entering the furnace, thus making it practicallynecessary for an empty position to be between the discharging positionand the charging position. However, such an empty position is aninadequate design concept for modern heat treating applications. If arotary hearth furnace is mounted with a charging door and a separatedischarge door, radiant tubing in the area of said empty position mayprovide a certain thermal separation between the furnace charging zoneand the furnace discharging zone. It would also be possible to separatethe two zones by a baffle if arrangements are made for returning trayswithout their inserts from the discharging position to the chargingposition. Further, large rotary hearth furnaces include a large unusedarea in their center since it is impossible to separate cold atmospherefrom hot atmosphere. In order to eliminate some of the disadvantagesdescribed, pusher-type furnaces have been used for continuously treatingmetal in a gaseous atmosphere. However, the surface area required forthe installation of such pusher-type furnaces is considerable. Also, thechambers of pusher-type furnaces are large and therefore the energyinput for heat-treating the metal pieces is high.

Additionally, trays and tray inserts for pusher-type furnaces accountfor some 20 to 50% of the gross charge weight. In the case of apusher-type furnace they must be made of heat-resistant material andwill be heated and cooled during each journey through the furnace, thusincreasing energy consumption, and subjecting them to early wear.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for a furnace thatovercomes the aforementioned problems of the prior art pusher-typefurnace for treating metal pieces in a controlled atmosphere. This isaccomplished increasing furnace throughput without increasing the sizeof the furnace and still reducing energy consumption.

It is another object of the present invention to provide a furnaceincorporating a circular conveyor system, that includes a plurality ofcharge support elements moveable with respect to each other in both thevertical direction and the direction of charge travel. The supportelements may be arranged radially or in a circle. Part of said supportelements are fixed along the inner circumference of said circular chargeconveyor system and part of said charge support elements are fixed alongthe outer circumference of said charge conveyor system so that a firstgroup of support elements so fixed along said inner circumference and asecond group of support elements so fixed along said outer circumferencemay be lifted and lowered and rotated relative to each other. Thesupport elements within each such group are angularly spaced. Thisangular spacing may be sufficiently wide for the groups of such supportelements to. If the support elements are arranged radially, several suchelements may be grouped to form fork-shaped elements.

In a preferred embodiment of the present invention, the charge supportelements, consisting of bars or fork-shaped elements, are arranged inseveral planes laid out in the vertical direction. Further, the conveyorsystem is divided along its circumferential length into a plurality ofsegments. Each segment includes at least one of the corresponding innercircumference support elements and between at least one of thecorresponding outer circumference support elements. To form at leastpart of a helical arrangement of the conveyor system, at least twoadjacent segments are spaced vertically apart from one another, so eachsegment is in a different plane extending horizontally with respect tothe central axis of the furnace. If all of the support elements aregrouped into these segments, then a stain-like arrangement of theconveyor system could be formed, such that a continuous or discontinuoushelical path of travel of the workpieces inside the furnance is created.Then, as a workpiece is transferred from one horizontal plane to adifferent horizontal plane, the workpiece is also carried forward in thedirection of charge travel.

In accordance with the present invention, the group of support elementsfixed along the inner circumference or the group of support elementsfixed along the outer circumference of the conveyor system may belifted, lowered and moved in a circular direction. It is also possiblefor some of said support elements to be lifted or lowered and some othersupport elements to be moved in a circular direction. These movementscause the charge to be carried forward by the conveyor system of thefurnace. In the case of a helical arrangement the charge may also becarried upwardly or downwardly in addition to being carried forward, inthe direction of charge travel.

In a preferred embodiment of the present invention, the furnace isequipped with an additional center cylinder also mounted with chargesupport elements. The elements facing the inner furnace area interactwith the elements fixed along the inner furnace circumference and theelements facing the outer furnace area interact with the elements fixedalong the outer circumference and facing the inner furnace area. If saidcenter cylinder is designed for lifting, lowering and rotating movement,the travel of the charge through the inner part of the conveyor systemmay be in the upward direction and the travel of the charge through theouter part of the conveyor system may be in the downward direction, thesupport elements forming a type of helical arrangement. In a furtherembodiment, the lifting, lowering and rotating movement may be by theinner and the outer cylinders in lieu of the center cylinder.

In accordance with the invention each charge support element does notcarry more than one piece to be heat-treated, and therefore the materialof said support elements may be ceramic. Further no trays are requiredfor carrying the charge through the furnace, although small baskets maypreferably be used for charging bulk material for heat treatment.

In another embodiment of the present invention, the atmosphere in thefurnace chamber is circulated by one or several fans mounted in theupper or lower furnace areas. Atmosphere circulation may be facilitatedby the arrangement of appropriate atmosphere outlet openings in theinner cylinder. Further the shafts of any such fans may be of the hollowtype for the installation of temperature or oxygen probes through suchhollow shafts.

Since the furnace chamber will usually be limited by the inner and theouter cylinders and since the furnace chamber may be isolated fromambient air, the furnace provided for by this invention may easily beused for treating metal pieces in a controlled atmosphere and even if noinner or outer cylinder is provided, an additional wall may easily bemounted.

These and other objects and features of the present invention will nowbe described, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a conveyor system mounted with radially arrangedbars;

FIG. 2 is a section along the II--II line of FIG. 1;

FIG. 3 is a view similar to FIG. 1 showing bars arranged radially;

FIG. 4 is a section of a furnace embodying the present invention;

FIG. 5 is another embodiment of a furnace in accordance with the presentinvention;

FIG. 6 is another embodiment of a charge support system arrangedradially;

FIG. 7 is an embodiment of the present invention showing a doublehelical arrangement;

FIGS. 8 and 9 represent lines of several furnaces in accordance with thepresent invention; and

FIGS. 10a and 10b are sections along the X--X line in FIG. 3.

Referring first to FIG. 1, the schematic shows part of a conveyorsystem. The charge support elements fixed to the inner cylinder 1 areangularly spaced bars 2 arranged radially and protruding towards theouter furnace area. Similar bars 4 of a corresponding arrangement, butprotruding towards the inner furnace area are mounted to the outercylinder 3. Bars 2 and 4 can be equal strength. A piece to be treated 5which is represented by broken lines and may, by way of example, be of acircular shape rests on said bars. If bars 2 and 4 are moved relative toeach other by lifting, moving in a circular direction and lowering,piece 5 will travel in the direction of arrow 6. Further, the points ofsupport on which the pieces rest, change continuously as a result of themode of charge travel, thus eliminating the risk of inadequate heattreatment of piece 5 at such support points.

The section along the II--II line of FIG. 1 shown by FIG. 2 presents thevertical arrangement of the conveyor system invented. The bars 2 mountedto the inner cylinder 1 and the bars 4 mounted to the outer cylinder 3carry piece 5. If the height of said piece is H and the height of saidbars is h, the distance A between piece 5 and the bars 2 and 4 abovesaid piece 5 will have to be greater than height h for pieces not totouch each other during the movement of rotation.

FIG. 3 also shows part of the conveyor system, but the charge supportelements mounted to the inner cylinder 1 are fork-shaped or hair pinshaped elements 7 in lieu of bars, said fork-shaped elements protrudingtowards the outer furnace area. The and the support elements mounted tothe outer cylinder 3 are corresponding fork-shaped elements 8 protrudingradially to the inner furnace area. Said conveyor system operates asdescribed above for the conveyor system shown by FIG. 1 and as in FIG.1, the charge 5 is shown by broken lines.

Whereas FIGS. 1 and 3 show the circular arrangement of the conveyorsystem, the figures do not show the horizontal cross-section of thefurnace, a circular horizontal furnace cross-section like the horizontalcross-section of the circular conveyor system minimizing heat loss, butbeing usually difficult to manufacture. The furnace shape will hencepreferably be hexagonal or octagonal rather than tetragonal even if atetragonal furnace shape would also represent an embodiment of thepresent invention.

FIG. 4 is a longitudinal section of an embodiment of the presentinvention. Bars 2 protruding radially to the outer furnace area areagain mounted to the inner cylinder 1 and corresponding bars 4protruding radially to the inner furnace area are mounted to the outercylinder 3, said bars carrying pieces to be treated 5. The furnaceembodied in FIG. 4 is heated by burners 9. The outer cylinder 3 mayseparate the burner zone 10 from the heat treatment chamber 11 toeliminate any effect of flue gas on the atmosphere in the furnacechamber 11. The inner cylinder 1 is provided with openings 22 forventilation or for the introduction of certain gases into the furnacechamber.

In the embodiment of the present invention shown by FIG. 4, a motor 12located below the inner cylinder 1 provides the lifting, lowering androtating movement for inner cylinder 1 that causes support elements 7 tobe lifted, lowered, and moved in a circular direction. A hollow shaft 13is provided in the upper part of the arrangement for the measurement ofthe temperature and the oxygen content of the furnace atmosphere byprobes that are introduced to the furnace atmosphere through shaft 13.Certain gases can also be introduced into the furnace chamber throughshaft 13. As can be seen in FIG. 4, a motor 60 is provided to driveshaft 13 in rotation through drive connection 61. Bearings 62 areprovided to mount shaft 13 for rotation. Preferably, a fan 63 is mountedon shaft 13 for fixed rotation therewith.

In FIG. 4, the conveyor system is laid out in a helical arrangement. Thefurnace is charged from the top in a manner not shown and the pieces 5to be treated travel downwardly along the helically arranged conveyorsystem. At the lower end of the furnace, pieces 5 are picked up by a rod14 and then introduced into ducting 15 for a subsequent transfer of thetreated charge by a mechanism not shown to an oil quench tank or adownstream furnace. The helical arrangement depicted may be continuedfurther in the downward direction for direct transfer to the conveyormechanism of ducting 15.

If the embodiment of the present invention depicted by FIG. 4 iscompared with a pusher-type furnace and if the assumption is made that acharge volume of approx. 2 m³ is desired, the necessary furnace chambervolume of 30 m³ in the case of a pusher-type furnace and 10 m³ in thecase of a furnace of the type depicted by FIG. 4, hence reducing thefurnace chamber volume required for handling the same charge volume to1/3rd and thus also reducing the quantity of bricks needed forconstructing the furnace to 1/3rd. Moreover, the surface area requiredfor the installation of the furnace is decreased by half and the energyrequired for maintaining the furnace temperature while the furnace isidle (idle furnace consumption) is lowered from approx. 120 kW in thecase of a pusher furnace to 1/3rd or approx. 40 kW in the case of afurnace of the type depicted by FIG. 4.

FIG. 5 shows another embodiment of the present invention. The parts ofFIG. 5 that are similar to the parts of FIG. 4 are indicated with likereference numbers. Motor 12 is located below the furnace as in theembodiment of the invention shown by FIG. 4. However, the furnacedepicted by FIG. 5 consists of two temperature zones, the heating zone16 and the soaking zone 17. Atmosphere circulation to said two zonesalso differs in accordance with the different functions of said twozones. The atmosphere for chamber 18 of the soaking zone 17 flowsthrough a hollow shaft that enters chamber 18 through opening 22 andreturn to the furnace area inside the inner cylinder 1 through opening23. The atmosphere for the heating zone chamber 19 is provided in asimilar manner as depicted by FIG. 5. The atmosphere for the heatingzone usually differs from the atmosphere for the soaking zone. In FIG. 5a fan 63 is provided at each end of the furnace, one in each of the twotemperature zones 16 and 17. The fans are provided with suitable drivemeans as discussed with respect to the FIG. 4 embodiment.

FIG. 6 shows an embodiment of the present invention differing from theembodiments shown by FIGS. 1 and 2, the inner and outer cylinder wallsbeing replaced by columns 20 and 21 with columns 21 being arranged alongthe inner circumference and columns 20 being arranged along the outercircumference of the furnace. The cross-sections of said columns arehexagonal and said columns may consist of hollow or solid sections. Thefork-shaped or hairpin shaped elements 24 are placed on said columns andif the column 21 part of the conveyor system is raised, moved in acircular path and lowered, the piece to be treated is moved as discussedin the description of FIG. 1. The embodiment of the present inventionshown by FIG. 6 is particularly suited for the use of ceramic chargesupport elements and, if necessary, an additional wall may be providedbetween the furnace chamber proper and the burner area or the furnacechamber proper and the inner furnace area, which may thereby be used foratmosphere circulation. The columns may be of any cross-section, but ifsaid columns consist of sections with a circular cross-section, it willbe necessary to provide for grooves or ribs to arrest the fork-shapedelements and to prevent movement around the column.

FIG. 7 shows an embodiment of the present invention in which the furnaceconveyor system arrangement is of the double helix type. Similar to thearrangements shown by FIGS. 1 and 3, bars 29 are mounted toward an innercylinder 25 and protrude radially to the outer furnace area, and bars 32are mounted to an outer cylinder 28 and protrude radially toward theinner furnace area. Additionally, a center cylinder 27 has mountedthereon bars 30 protruding radially toward the inner furnace area andbars 31 protruding radially toward the outer furnace area. The pieces tobe treated 33 and 34 rest on bars 30 and 31. Center cylinder 27 rotatesabout the same point of rotation as the other two cylinders referred toand is also lowered and lifted. Rotation of cylinder 27 provides bars 30and 31 with movement along a circular path. Following the circularmovement, piece 33 is placed on bar 29 and piece 34 is placed on bar 32.Preferably, the pieces enter the furnace at the bottom of the outerhelical arrangement and leave the furnace at the bottom of the innerhelical arrangement. At the top ends of the two helically arrangedconveyor systems, piece 35 is moved into position 36 where it isreceived by the inner helically arranged system. The furnace chargingoperation may differ from the mode presented above and the charge mayenter the furnace through the inner helically arranged system and leavethe furnace from the outer helically arranged system. Charging may befrom the top, or from the bottom as shown by FIG. 7. The first part ofthe charge travel through the furnace will usually be for heating thecharge while the latter part using for example, the inner helicallyarranged system as shown by FIG. 7, will be for charge soaking.

FIGS. 8 and 9 show the combined use of several of the furnaces which arethe object of the present invention. Furnace 42 is used for heating,furnace 41 for soaking and furnace 40 is operated at a lowertemperature, with quench bath 47 being provided for hardening. Furnace42 is charged as shown by arrow 43 and the charge leaving said furnaceat the bottom end of the helically arranged conveyor system istransferred through duct 44 to furnace 41 where said charge travels inan upward direction and is then transferred through duct 45 to furnace40. Following travel through furnace 40, the charge leaves said furnaceas shown by arrow 46 for transfer to the quench bath 47.

FIGS. 10a and 10b are sections along the X--X line of FIG. 3. FIG. 10ashows the fork-shaped elements 7 mounted to the unrolled wall 1 of theinner cylinder. The mounting elements 51, which may be termed flanges,carry the charge support elements 7 at their ends not facing said wall.Said support elements 7 and the support elements 8 mounted to the outercylinder 3 move the pieces to be treated 5. In the embodiment of theinvention shown, to carry the charge forward, the inner cylinder withthe support elements 7 mounted thereon is lifted, rotated and lowered,while the outer cylinder 3 corresponding support elements 8 remainsstationary.

The travel of charge 5 is explained with reference to FIG. 10b. Prior tothe lifting, lowering and rotating movements of cylinder 1, all supportelements are in their initial positions as shown in the top left cornerof FIG. 10b. Support elements 7, mounted to the inner cylinder, aredesignated as a through d. The movement of the ends of said supportelements 7 is described below. Upon the commencement of said movement,said elements are in the initial position indicated by points a0 and d0,the support elements 7 and 8 extending radially toward each other andextending in between each other. The top left point of the charge isdesignated m and the top right point of the charge is designated n,their initial positions being indicated m0 and n0 respectively. Aselements 7 raised, all pieces to be treated are first lifted and thencarried forward by rotation of inner cylinder 1. The description belowwill merely explain, by way of example, the movement of the top leftpiece. Following the lifting operation, the bottom ends of the elementsare at points a1 and a2, while the top corners of piece 5 are at pointsm1 and n1. During the circular movement, the elements a to d move to theright carrying piece 5 forward, the circular movement ending when theends of elements a to d have reached points a2 and d2 and the topcorners of piece 5 have reached points m2 and n2. As the elements 7 arethen lowered, piece 5 is placed on element 8 fixed to the outercylinder, as the elements 7 reach points a3 and d3 and the top cornersof piece 5 reach points m3 and n3. The elements 7 then continue to belowered until they reach points a4 and d4. Through the ensuing rotationof cylinder 1, the elements 7 then move to the left to points a5 and d5,the rotating movement then ending and the elements being again raised totheir initial positions a0 and d0 for a new cycle to commence. Duringthe period while the elements return from points a3 to d3 to points a0and d0, piece 5 will continue to be carried by elements 8, the uppercorners of piece 5 resting in the same positions m3, m4, m5 and p0 andn3, n4, n5 and q0 respectively. During the next lifting cycle, thecenter piece will only be raised to points p1 and q1, since it will bemoved to the lower position on the right hand side.

FIGS. 10a and 10b depict a stair-type arrangement of the charge supportelements. In another embodiment, such arrangement may be level, but iffork-type elements are used, a stair-type arrangement is preferablyselected.

FIGS. 1 through 9 merely depict, by way of example, several embodimentsof the present invention. Downward travel may, for example, also beachieved by rollers on which the charge travels downward due to its ownweight. It is hence unnecessary to provide for bars for downward travel.

The ducting at the inlet and the outlet of the furnace shown in FIGS. 8and 9 may be replaced by ducting connected to the heating zone 16 or thesoaking zone 17 of a furnace of the type shown by FIG. 5 for achievingdifferent temperature curves during heating or soaking.

To increase furnace throughput, the two helical arrangements shown byFIG. 7 may be arranged for charge travel in the same upward or downwarddirection.

Obviously many modifications and variations of the present invention arepossible in light of the above teachings. Thus it is to be understoodthat within the scope of the appended claims, the inventor may bepracticed then as specifically described.

What we claim is:
 1. A furnace for heating workpieces comprising:afurnace chamber having a vertical central axis; means for charging anddischarging the workpiece to and from said furnace chamber; conveyormeans arranged substantially concentrically with respect to said axis,for conveying the workpieces within at least a portion of said furnacechamber; said conveyor means comprising a first group and a second groupof radially extending open ended workpiece support elements, said firstgroup of support elements being movable relative to said second group ofsupport elements in substantially vertical directions parallel withrespect to said axis and in substantially circular directions concentricwith respect to said axis such that said relative movement provides stepwise travel of the workpiece in a direction of travel concentric withsaid axis, the workpiece being supported alternately by said first andsaid second group of support elements at alternating points ofengagement along the bottom suface of the workpieces; said conveyormeans having radially separated inner and outer portions; first mountingmeans for supporting said first group of support elements and secondmounting means for supporting said second group of support elements;said first group of support elements being mounted on said firstmounting means along said inner portion of said conveyor means and saidsecond group of support elements being mounted on said second mountingmeans along said outer portion of said conveyor means; at least one ofsaid mounting means being movable to provide said relative movementbetween said groups of said support elements; and said relative movementbeing defined by first vertical relative movement between said first andsaid second groups of support elements, second lateral relative movementalong a circular path of travel relative to said axis between said firstand said second group of support elements, and third vertical movementbetween said first and said second groups of support elements such thateach element of one of said groups is raised above and lowered below atleast one element of the other of said groups and further such that saideach element passes at both sides laterally of said at least one elementin a closed loop during one cycle of said relative movement between saidfirst and said second groups of said support elements.
 2. The furnace ofclaim 1, further including motor means for driving said at least onemovable mounting means to cause said relative movement in directionsparallel to and concentric with said axis between said first and saidsecond groups of support elements.
 3. The furnace according to claim 1,wherein at least one of said groups of support elements comprise barelements having opposed ends, said bar elements being mounted to saidmounting means at one of said ends.
 4. The furnace according to claim 3,wherein said bar elements are arranged in equal circumferential spacingalong said inner and said outer portions of said conveyor means.
 5. Thefurnace according to claim 1, wherein said conveyor means is arranged inthe shape of a circle having an origin intersecting with said axis. 6.The furnace according to claim 3, wherein said bars are further groupedtogether and arranged within separate adjacent sectors along each ofsaid inner and said outer portions of said conveyor means.
 7. Thefurnace according to claim 1 further including fork shaped elementscomprising at least two of said support elements and being arrangedwithin separate adjacent sectors along each of said inner and outerportions of said conveyor means, said fork shaped elements furtherincluding mounting means for mounting said fork shaped elements to oneof said inner and said outer mounting means.
 8. The furnace according toclaim 3, wherein said bar elements of said first group are arranged in aplane extending horizontally with respect to said axis, and said barelements of said second group are arranged in a plane extendinghorizontally with respect to said axis.
 9. The furnace according toclaim 7, wherein said fork elements of said first group are arranged ina plane extending horizontally with respect to said axis, and said forkelements of said second group are arranged in a plane extendinghorizontally with respect to said axis.
 10. The furnace according toclaim 1, wherein said first mounting means is movable to cause saidrelative movement in directions parallel to and concentric with saidaxis between said first and said second groups of support elements, andsaid second mounting means is stationary relative to said first mountingmeans.
 11. The furnace according to claim 1, wherein said first mountingmeans comprises a cylinder arranged concentrically with said axis. 12.The furnace according to claim 1, wherein said second mounting meanscomprises a cylinder arranged concentrically with said axis.
 13. Thefurnace according to claim 1, further comprising:said furnace chamberhaving vertically separated top and bottom portions; and said first andsaid second mounting means comprise a plurality of columns extendingbetween said top and said bottom furnace portions, said columns beingsubstantially parallel to said axis.
 14. The furnace according to claim1 further comprising:said furnace chamber including top and bottomportions; and one of said first or said second mounting means comprisesa plurality of columns extending between said top and said bottomportions of said furnace and the other of said first and said secondmounting means comprising a cylinder extending between said bottom andsaid top portions of said furnace.
 15. The furnace according to claim 1,wherein said discharging means includes means for conveying theworkpieces to a quench bath.
 16. The furnace according to claim 1,wherein said furnace chamber comprises a continuous tubular structuresuitable for containing a gas, said furnace chamber further including atleast one fan means for circulating the gas.
 17. The furnace accordingto claim 2, further comprising: top and bottom end portions, and saidmotor means being located at said bottom end portion of said furnace.18. The furnace according to claim 1, wherein said conveyor means isarranged helically about said axis.
 19. The furnace according to claim1, wherein said conveyor means is divided along its circumferentiallength into a plurality of segments, each of said segments including atleast one element of said first group of support elements and at leastone element of said second group of support ements, and at least two ofsaid segments are spaced vertically apart from one another, such that asa workpiece advances along said conveyor means from one said segment toan adjacent and vertically spaced said segment, the workpiece istransferred from one horizontal plane to a different horizontal planewith respect to said axis.
 20. The furnace according to claim 19,wherein each of said segments exists in a horizontal plane spacedvertically from an adjacent said segment such that a continuous helicalarrangement of said conveyor means is provided and so further that theworkpieces are conveyed from said charging means to said dischargingmeans in a helical path of travel.
 21. The furnace according to claim 1,further comprising:said conveyor means being arranged helically aboutsaid axis; said furnace chamber having top and bottom portions; and saidfirst and said second mounting means comprises first and secondcylinders extending between said top and said bottom portions of saidfurnace chamber.
 22. The furnace according to claim 1, furthercomprising:said conveyor being arranged helically about said axis; andfork-shaped elements comprising at least two of said support elementsand being arranged within separate adjacent sectors along each of saidinner and outer portions of said conveyor means, said fork-shapedelements furthing including mounting means for mounting said fork-shapedelements to one of said inner and said outer mounting means.
 23. Thefurnace according to claim 18, wherein at least one of said groups ofsupport elements comprise bar elements having opposed ends, one of saidends being mounted to said mounting means.
 24. The furnace according toclaim 1 further comprising:said conveyor means being arranged helicallyabout said axis; said furnace chamber including top and bottom portions;and said first and said second mounting means comprising columnsextending between said top and said bottom portions of said furnacechamber.
 25. The furnace according to claim 13, furthercomprising:fork-shaped elements comprising at least two of said supportelements, said fork-shaped elements further including mounting means formounting said fork-shaped elements to said columns; said mounting meansfor said fork-shaped elements including means for encircling thecircumference of said columns; and said columns further having apolygonal cross-sectional shape for preventing relative rotationalmovement between said fork-shaped elements and said columns.
 26. Thefurnace according to claim 14, further comprising:fork-shaped elementscomprising at least two of said support elements, said fork-shapedelements further including mounting means for mounting said fork-shapedelements to said columns; said mounting means for said fork-shapedelements including means for encircling the circumference of saidcolumns; and said columns further having a polygonal cross-sectionalshape for preventing relative rotational movement between saidfork-shaped elements and said columns.
 27. The furnace according toclaim 24, further comprising:fork-shaped elements comprising at leasttwo of said support elements, said fork-shaped elements furtherincluding mounting means for mounting said fork-shaped elements to saidcolumns; said mounting means for said fork-shaped elements includingmeans for encircling the circumference of said columns; and said columnsfurther having a polygonal cross-sectional shaped for preventingrelative rotational movement between said fork-shaped elements and saidcolumns.
 28. The furnace according to claim 1 wherein one of said firstand said second mounting means is movable to cause said relativemovement in directions parallel to said axis, and the other of saidfirst and second mounting means is movable to cause said relativemovement in directions concentric with said axis, such that saidrelative movement between said first and said second groups of supportelements is achieved by a combined movement of both said first and saidsecond mounting means.
 29. A furnace for heating workpieces comprising:afurnace chamber having a vertical central axis; means for charging anddischarging the workpieces to and from said furnace chamber; conveyormeans arranged substantially concentrically with respect to said axis,for conveying the workpieces within at least a portion of said furnacechamber; said conveyor means comprising a first group of workpiecesupport elements and a second group of workpiece support elements, saidfirst group of support elements being movable relative to said secondgroup of support elements in substantially vertical directions parallelwith respect to said axis and in substantially circular directionsconcentric with respect to said axis such that said relative movementprovides step wise travel of the workpiece in a direction of travelconcentric with said axis, the workpieces being supported alternately bysaid first and said second group of support elements at alternatingpoints of engagement along the bottom surface of the workpieces; saidfurnace chamber including fan means for circulating the atmospherewithin said furnace chamber, said fan means including a hollow driveshaft that extends into the interior of said furnace chamber fromoutside of said furnace chamber such that temperature and oxygen probesmay be inserted into said furnace chamber through said hollow driveshaft.
 30. A plurality of furnaces for heating workpieces, each of saidfurnaces comprising:a furnace chamber having a vertical central axis;means for charging and discharging the workpieces to and from saidfurnace chamber; conveyor means arranged substantially concentricallywith respect to said axis for conveying the workpieces within at least aportion of said furnace chamber; said conveyor means comprising a firstgroup of radially extended open ended workpiece support elements and asecond group of radially extending open ended workpiece supportelements, said first group of support elements being movable relative tosaid second group of support elements in substantially verticaldirections parallel with respect to said axis and in substantiallycircular directions concentric with respect to said axis such that saidrelative movement provides step wise travel of the workpieces in adirection of travel concentric with said axis, the workpieces beingsupported alternatively by said first and said second group of supportelements at alternating points of engagement; said relative movementbeing further defined by first vertical relative movement between saidgroups of support elements, second lateral relative movement along acircular path of travel relative to said axis between said groups ofsupport elements, and third vertical movement between said groups ofsupport elements such that each support element of one of said groups israised above and lowered below at least one support element of the otherof said groups and further such that said each support element passes atboth sides laterally of said at least one support element in a closedloop during one cycle of said relative movement between said groups ofsaid bar elements; said plurality of furnaces comprising at least afirst heating furnace, a second soaking furnace, and a third lowtemperature furnace, each of said furnaces being connected to oneanother.
 31. The furnace according to claim 30, further including aquench bath arranged adjacent to said discharge means of said lowtemperature furnace.
 32. A furnace for heating workpieces comprising:afurnace chamber having a vertical central axis; means for charging anddischarging workpieces to and from said furnace chamber; conveyor meansarranged substantially concentrically with respect to said axis andbeing further arranged helically about said axis for conveying theworkpieces within at least a portion of said furnace chamber; saidconveyor means comprising a first group workpiece support elements and asecond group of workpiece support elements, said first group of supportelements being movable relative to said second group of support elementsin substantially vertical directions parallel with respect to said axisand in substantially circular directions concentric with respect to saidaxis such that said relative movement provides step wise travel of theworkpieces in a direction of travel concentric with said axis, theworkpieces being supported alternately by said first and said secondgroup of support elements at alternating points of engagement; saidconveyor means having radially separated inner and outer portions; saidfurnace chamber including top and bottom portions; an inner cylinderextending between said top and said bottom portions of said furnacechamber and an outer cylinder extending between said top and said bottomportions of said furnace chamber; said support elements of said firstgroup being mounted on said inner cylinder along said inner portion ofsaid conveyor means and projecting substantially radially outwardlytoward said outer cylinder, and said support elements of said secondgroup being mounted to said outer cylinder along said outer portion ofsaid conveyor means and projecting substantially radially inwardlytoward said inner cylinder; said inner cylinder being mounted formovement with respect to said outer cylinder to provide said relativemovement between said groups of said support elements, said cylindermovement being provided by a motor mounted adjacent to said bottomportion of said furnace chamber in driving engagement with said innercylinder; and said furnace chamber being divided into upper and lowertemperature zones, fan means mounted within said upper portion of saidfurnace chamber for circulating the atmosphere of said upper temperaturezone, and fan means mounted in said lower portion of said furnacechamber for circulating the atmosphere in said lower temperature zone.33. The furnace according to claim 32, wherein each of said fan meansincludes a hollow drive shaft that extends into the interior of saidfurnace chamber from outside of said furnace chamber so that probes maybe inserted into said furnace chamber through said hollow drive shaft.34. A furnace for heating workpieces comprising:a furnace chamber havinga vertical central axis; means for charging and discharging theworkpieces to and from said furnace chamber; conveyor means arrangedsubstantially concentrically with respect to said axis and being furtherarranged helically about said axis for conveying the workpieces withinat least a portion of said furnace chamber; said conveyor meansincluding a first inner helically arranged portion and a second outerhelically arranged portion; said conveyor means further comprising afirst group of workpiece support elements and a second group ofworkpiece support elements, said first group of support elements beingmoveable relative to said second group of support elements insubstantially vertical directions parallel with respect to said axis andin substantially circular directions concentric with respect to saidaxis such that said relative movement provides stepwise travel of theworkpieces in a direction of travel concentric with said axis, theworkpieces being supported alternately by said first and said secondgroup of support elements at alternating points of engagement; saidconveyor means having radially separated inner and outer portions; saidfurnace chamber including top and bottom portions; inner mounting meansfor supporting a portion of said first group of support elements andouter mounting means for supporting a portion of said second group ofsupport elements; at least one intermediate mounting means forsupporting a portion of each of said first and said second group ofsupport elements; said first group of support elements that are mountedon said inner mounting means being mounted on said inner mounting meansalong said inner portion of said conveyor means and projectingsubstantially radially outwardly toward said outer portion of saidconveyor means, and said second group of support elements that aremounted on said outer mounting means being mounted on said outermounting means along said outer portion of said conveyor means andprojecting substantially radially inwardly toward said inner portion ofsaid conveyor means, and said first group of support elements mounted onsaid intermediate mounting means being mounted along said inner portionof said conveyor means and projecting substantially radially outwardlytoward said outer portion of said conveyor means and said second groupof support elements mounted on said intermediate mounting means beingmounted on said intermediate mounting means along said outer portion ofsaid conveyor means and projecting substantially radially inwardlytoward inner portion of said conveyor means; and at least one of saidmounting means being movable to provide said relative movement betweensaid groups of support elements.
 35. The furnace according to claim 34,wherein only one intermediate mounting means is provided and furthersaid intermediate mounting means is movable in directions parallel tosaid axis and in directions circular with respect to said axis toprovide said relative movement.
 36. The furnace according to claim 34,wherein at least one of said groups of support elements comprise barelements having opposed ends, said bar elements being mounted to saidmounting means at one of said ends.
 37. The furnace according to claim34, wherein at least one of said groups of support elements comprisefork-shaped elements having opposed end portions, one of said endportions being mounted to said mounting means.
 38. The furnace accordingto claim 34, further comprising:said conveyor means being divided alongits circumferential length into a plurality of segments, each of saidsegments including at least one element of said first group of supportelements and at least one element of said second group of supportelements, and at least two of said segments being spaced verticallyapart from one another, such that as a workpiece advances along saidconveyor means from one said segment to another vertically spaced saidsegment, the workpiece is transferred from one horizontal plane to adifferent horizontal plane with respect to said axis.
 39. The furnaceaccording to claim 34, wherein said conveyor means is divided into aninner helically arranged portion and an outer helically arrangedportion, said inner helically arranged portion of said conveyor meansextending between said inner mounting means and said intermediatemounting means, and said outer helically arranged portion extendingbetween said intermediate mounting means and said outer mounting means,such that as a workpiece is charged from said charging means, theworkpiece travels upwardly in a helical direction of travel along saidouter helically arranged portion of said conveyor means and thendownwardly in a helical direction of travel along said inner helicallyarranged portion of said conveyor means toward said discharge means. 40.The furnace according to claim 34, wherein each of said mounting meanscomprises a cylinder arranged concentrically with said axis.
 41. Thefurnace according to claim 34, wherein said relative movement is furtherdefined by first vertical relative movement between said first group ofsupport elements and said second group of support elements, secondlateral relative movement along a circular path of travel relative tosaid axis between said first group of support elements and said secondgroup of support elements, and third vertical movement between saidgroups of support elements such that a workpiece is first supported byboth said groups of support elements, second supported by one of saidgroups of support elements and third again supported by both said groupsof support elements.
 42. A furnace for heating workpieces, comprising:afurnace chamber having a vertical central axis; means for charging anddischarging workpieces to and from said furnace chamber; conveyor meansarranged substantially concentrically with repect to said axes and beingfurther arranged helically about said axis for conveying the workpieceswithin at least a portion of said furnace chamber; said conveyor meanscomprising a first group of workpiece support elements and a secondgroup of workpiece support elements, said first group of supportelements being movable relative to said second group of support elementsin substantially vertical directions parallel to said axis and insubstantially circular directions concentric to said axis such that saidrelative movement provides step-wise travel of the workpieces in adirection of travel concentric with said axis, the workpieces beingsupported alternatively by said first and said second group of supportelements at alternating points of engagement; said conveyor means havingradially separated inner and outer portions; said furnace chamberincluding top and bottom portions; inner mounting means extendingbetween said top and said bottom portions of said furnace chamber andouter mounting means extending between said top and said bottom portionsof said furnace chamber; said support elements of said first group beingmounted on said inner mounting means along said inner portion of saidconveyor means and projecting substantially radially outwardly towardsaid outer mounting means, and said support elements of said secondgroup being mounted to said outer mounting means along said outerportion of said conveyor means and projecting substantially radiallyinwardly toward said inner mounting means; said inner mounting meansbeing mounted for movement with respect to said outer mounting means toprovide said relative movement between said groups of said supportelements, said mounting means movement being provided by a motor mountedadjacent to said bottom portion of said furnace chamber in drivingengagement with said inner mounting means; and said furnace chamberbeing divided into upper and lower temperature zones, fan means mountedwithin said upper portion of said furnace chamber for circulating theatmosphere of said upper temperature zone, and fan means mounted in saidlower portion of said furnace chamber for circulating the atmosphere insaid lower temperature zone.
 43. The furnace according to claim 42,further comprising:said furnace chamber including top and bottomportions; and said first and said second mounting means comprisingcolumns extending between said top and said bottom portions of saidfurnace chamber.
 44. The furnace according to claim 42, furthercomprising:said furnace chamber including top and bottom portions; andone of said first or said second mounting means comprises a plurality ofcolumns extending between said top and said bottom portions of saidfurnace and the other of said first and said second mounting meanscomprises a cylinder extending between said bottom and said top portionsof said furnace.
 45. The furnace according to claim 43, furthercomprising:fork-shaped elements comprising at least two of said supportelements, said fork-shaped elements further including mounting means formounting said fork-shaped elements to said columns; said mounting meansfor said fork-shaped elements including means for encircling thecircumference of said columns; and said columns further having apolygonal cross-sectional shape for preventing relative rotationalmovement between said fork-shaped elements and said columns.
 46. Furnaceaccording to claim 42, wherein each of said fan means includes a hollowdrive shaft that extends into the interior of said furnace chamber fromoutside of said furnace chamber so that probes may be inserted into saidfurnace chamber through said hollow drive shaft.
 47. Furnace accordingto claim 43, wherein each of said fan means includes a hollow driveshaft that extends into the interior of said furnace chamber fromoutside of said furnace chamber so that probes may be inserted into saidfurnace chamber through said hollow drive shaft.
 48. Furnace accordingto claim 44, wherein each of said fan means includes a hollow driveshaft that extends into the interior of said furnace chamber fromoutside of said furnace chamber so that probes may be inserted into saidfurnace chamber through said hollow drive shaft.
 49. Furnace accordingto claim 45, wherein each of said fan means includes a hollow driveshaft that extends into the interior of said furnace chamber fromoutside of said furnace chamber so that probes may be inserted into saidfurnace chamber through said hollow drive shaft.